Recently, touch pads have been widely adopted as operating devices in mobile devices, such as smartphones and tablets. A touch pad is a pointing device capable of pointing a coordinate by a user performing an operation by making a finger as a pointer in contact with the pad.
However, depending on a state of the finger when the user performs an operation on the touch pad, there are some cases where the pointed coordinate actually detected by the touch pad does not correspond to an operation intended by the user.
As a specific example, in a case where an operation is performed by moving the thumb from the wrist side to the fingertip side so as to protrude the thumb, the tip of the thumb is in contact with the touch pad when the operation is initiated. As the thumb is moved to the fingertip side from this state, the tip of the thumb is gradually warped upward and thus is detached from the touch pad, and the belly of the thumb becomes gradually in contact with the touch pad. Then, as the thumb is moved further to the fingertip side, the tip of the thumb is more warped, and thus the portion of the belly of the thumb in contact with the touch pad approaches toward the base of the thumb.
While moving the thumb in this way, the user has an image such that a fingertip corresponds to the pointed coordinate. However, at the time of this operation, the actual contact portion of the thumb with the touch pad moves from the fingertip of the thumb to the base side of the belly thereof, and the pointed coordinate detected by the touch pad also moves correspondingly. Thus, for example, when an operation is performed with the thumb, deviation is likely to occur between the operation intended by the user and the pointed coordinate actually detected by the touch pad.
For this reason, an input device such as the following one is known. In other words, the input device calculates a contact width D of a contact region in a vertical direction based on contact information concerning the touch pad, calculates a center coordinate y of the contact region, and further calculates the amount of correction D/N using the contact width D and a predetermined correction parameter N. Then, while the contact region is moving, the input device calculates the amount of movement of the contact point, using the corrected coordinate Y=y+D/N. While the contact region is stopped, the input device calculates the amount of movement, using the center coordinate of the contact region (see, for example, Patent Document 1).